The field of the invention is that of dental compositions. More precisely, the dental compositions used in the context of the present invention can be used for producing dental prostheses and for dental restoration.
Up until now, to produce dental compositions for the preparation of dental prostheses or of dental restoration materials, it is possible to use resins based on photopolymerizable acrylates. These ready-to-formulate products exhibit however upon use problems of irritation and potential problems of toxicity.
In addition, these products have the major disadvantage of causing high volume shrinkage during their polymerization, which makes their use complex and difficult for the production of dental prostheses or of dental restoration materials. Problems of attachment due to the volume shrinkage or to the lack of adherence of the polymers used are in particular observed.
The object of the present invention is to provide novel dental compositions which do not exhibit the disadvantages of the prior art. These novel dental compositions, which are polymerizable and/or crosslinkable in an oral environment, have markedly improved qualities, in particular as regards the very marked reduction in the phenomenon of shrinkage of the dental compositions used for the production of dental prostheses or of dental restoration materials.
The polymerizable and/or crosslinkable dental composition according to the invention comprises:
(1) at least one crosslinkable and/or polymerizable silicone oligomer or polymer which is liquid at room temperature or which is heat-meltable at a temperature of less than 100xc2x0 C., and which comprises:
at least one unit of formula (FS):
Zxe2x80x94SiRX0xe2x80x94O(3-a)/2
xe2x80x83in which:
a=0, 1 or 2,
R1, identical or different, represents an alkyl, cycloalkyl, aryl, vinyl, hydrogeno or alkoxy radical, preferably a C1-C6 lower alkyl,
Z, identical or different, is an organic substituent comprising at least one reactive epoxy, and/or alkenyl ether and/or oxetane and/or dioxolane and/or carbonate functional group, and preferably Z being an organic substituent comprising at least one reactive epoxy and/or dioxolane functional group,
and at least two silicon atoms,
(2) an effective quantity of at least one borate-type photoinitiator,
(3) at least one aromatic hydrocarbon photosensitizer with one or more aromatic nuclei which are substituted or not, having a residual light absorption of between 200 and 500 nm,
(4) and at least one dental filler present in a proportion of at least 10% by weight relative to the total weight of the composition.
According to a first advantageous variant of the present invention, the dental composition is polymerizable and/or crosslinkable under activation by the thermal route and/or by the photochemical route.
In general, the photochemical activation is carried out under UV radiation. More particularly, UV radiation having a wavelength of the order of 200 to 500 nm is used for the production of dental prostheses and UV-visible radiation having a wavelength greater than 400 nm for the production of restoration materials. A wavelength greater than 400 nm allows crosslinking and/or polymerization in an oral environment.
The silicone polymer or oligomer (1) has the advantage, compared with organic resins which are crosslinked by the cationic route, of being transparent to UV-visible light and therefore its use makes it possible to obtain materials which are very thick and whose photocrosslinking occurs in a short time.
The reactive functional groups Z of the silicone polymer or oligomer (1) may be highly varied. However, particularly advantageous dental compositions are obtained when the silicone oligomer or polymer (1) comprises at least one (FS) unit in which Z represents an organic substituent Z1 comprising at least one reactive epoxy, and/or dioxolane functional group, and preferably at least one reactive epoxy functional group.
According to two advantageous alternatives of the present invention, the silicone oligomer or polymer (1) with at least one reactive epoxy and/or dioxolane functional group Z1, and preferably at least one reactive epoxy functional group may:
(i) either comprise only this (these) type(s) of reactive functional group(s) Z1,
(ii) or comprise other reactive functional groups Z such as the reactive alkenyl ether, oxetane and/or carbonate functional groups Z2.
In the case of the first alternative (i), the dental composition may also comprise other silicone oligomers and/or polymers comprising other reactive functional groups Z2 such as alkenyl ether, oxetane and/or carbonate functional groups and optionally reactive functional groups Z1.
By way of examples of reactive functional groups Z, these may in particular be chosen from the following radicals: 
with Rxe2x80x3 representing a linear or branched C1-C6 alkyl radical.
According to a second advantageous variant of the present invention, the silicone polymer or oligomer consists of at least one silicone having the following average formula: 
The cationic photoinitiators are chosen from onium borates (taken on their own or as a mixture with each other) of an element of groups 15 to 17 of the Periodic Table [Chem. and Eng. News, vol. 63, No. 5, 26 of 4 Feb. 1985] or of an organometallic complex of an element of groups 4 to 10 of the Periodic Table [same reference].
The cationic entity of the borate is selected from:
(1) the onium salts of formula (I)
[(R1)nxe2x80x94Axe2x80x94(R2)m]xe2x88x92xe2x80x83xe2x80x83(I)
xe2x80x83in which formula:
A represents an element of groups 15 to 17 such as for example: I, S, Se, P or N,
R1 represents a carbocyclic or heterocyclic C6-C20 aryl radical, it being possible for said heterocyclic radical to contain, as heteroelements, nitrogen or sulfur,
R2 represents R1 or a linear or branched C1-C30 alkyl or alkenyl radical; said radicals R1 and R2 being optionally substituted with a C1-C25 alkoxy, C1-C25 alkyl, nitro, chloro, bromo, cyano, carboxyl, ester or mercapto group,
n is an integer ranging from 1 to V+1, v being the valency of the element A,
m is an integer ranging from 0 to vxe2x88x921 with n+m=v+1,
(2) the oxoisothiochromanium salts described in patent application WO 90/11303, in particular the sulfonium salt of 2-ethyl-4-oxoisothiochromanium or 2-dodecyl-4-oxoisothiochromanium,
(3) the sulfonium salts in which the cationic entity comprises:
31 at least one polysulfonium entity of formula (II.1): 
xe2x80x83in which:
the symbols Ar1, which are identical or different, each represent a monovalent phenyl or naphthyl radical, optionally substituted with one or more radicals chosen from: a linear or branched C1-C12, preferably C1-C6, alkyl radical, a linear or branched C1-C12, preferably C1-C6, alkoxy radical, a halogen atom, an xe2x80x94OH group, a xe2x80x94COOH group, an ester group xe2x80x94COO-alkyl where the alkyl portion is a linear or branched C1-C12, preferably C1-C6, residue, and a group of formula xe2x80x94Y4xe2x80x94Ar2 where the symbols Y4 and Ar2 have the meanings given just below,
the symbols Ar2, which are identical or different, each represent a monovalent phenyl or naphthyl radical, optionally substituted with one or more radicals chosen from: a linear or branched C1-C12, preferably C1-C6, alkyl radical, a linear or branched C1-C12, preferably C1-C6, alkoxy radical, a halogen atom, an xe2x80x94OH group, a xe2x80x94COOH group, an ester group xe2x80x94COO-alkyl where the alkyl portion is a linear or branched C1-C12, preferably C1-C6, residue,
the symbols Ar3, which are identical or different, each represent a divalent phenylene or naphthylene radical, optionally substituted with one or more radicals chosen from: a linear or branched C1-C12, preferably C1-C6, alkyl radical, a linear or branched C1-C12, preferably C1-C6, alkoxy radical, a halogen atom, an xe2x80x94OH group, a xe2x80x94COOH group, an ester group xe2x80x94COO-alkyl where the alkyl portion is a linear or branched C1-C12, preferably C1-C6, residue,
t is an integer equal to 0 or 1, with the additional conditions according to which:
when t=0, the symbol Y is then a monovalent radical Y1 representing the group of formula: 
xe2x80x83where the symbols Ar1 and Ar2 possess the meanings given above,
+when t=1:
 on the one hand, the symbol Y is then a divalent radical having the following meanings Y2 to Y4:
Y2: a group of formula: 
where the symbol Ar2 has the meanings given above,
Y3: a single valency bond,
Y4: a divalent residue chosen from:
xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, 

xe2x80x83a linear or branched C1-C12, preferably C1-C6, alkylene residue and a residue of formula xe2x80x94Si(CH3)2Oxe2x80x94,
 on the other hand, in the case solely where the symbol Y represents Y3 or Y4, the (terminal) radicals Ar1 and Ar2 possess, in addition to the meanings given above, the possibility of being linked to each other by the residue Yxe2x80x2 consisting of Yxe2x80x22 a single valency bond or of Yxe2x80x22 a divalent residue chosen from the residues cited in relation to the definition of Y4, which is inserted between the carbon atoms, opposite each other, situated on each aromatic ring at the ortho position with respect to the carbon atom directly linked to the cation S+;
32 and/or at least one monosulfonium entity possessing a single cationic center S+ per mol of cation and consisting, in most cases, of entity of formula (II.2): 
xe2x80x83in which Ar1 and Ar2 have the meanings given above in relation to formula (III.1), including the possibility of directly linking to each other only one of the radicals Ar1 to Ar2 in the manner indicated above in relation to the definition of the additional condition in force when t=1 in formula (II), calling into play the residue Yxe2x80x2;
(4) the organometallic salts of formula (III):
(L1L2L3M)xe2x88x92q
in which formula:
M represents a group 4 to 10 metal, in particular iron, manganese, chromium or cobalt,
L1 represents 1 ligand bound to the metal M by xcfx80 electrons, which ligand is chosen from the ligands xcex73-alkyl, xcex75-cyclopendadienyl and xcex77-cycloheptatrienyl and the xcex76-aromatic compounds chosen from the optionally substituted xcex76-benzene ligands and the compounds having from 2 to 4 condensed rings, each ring being capable of contributing to the valency layer of the metal M by 3 to 8 xcfx80 electrons;
L2 represents a ligand bound to the metal M by xcex7 electrons, which ligand is chosen from the ligands xcex77-cycloheptatrienyl and the xcex76-aromatic compounds chosen from the optionally substituted ligands xcex76-benzene and the compounds having from 2 to 4 condensed rings, each ring being capable of contributing to the valency layer of the metal M by 6 or 7 xcfx80 electrons;
L3 represents from 0 to 3 ligands, which are identical or different, linked to the metal M by "sgr" electrons, which ligand(s) is (are) chosen from CO and NO2xe2x88x92; the total electron charge q of the complex to which L1, L2 and L3 contribute and the ionic charge of the metal M being positive and equal to 1 or 2;
The anionic borate entity has the formula [BXaRb]xe2x88x92 in which:
a and b are integers ranging, for a, from 0 to 3 and, for b, from 1 to 4 with a+b=4,
the symbols X represent:
a halogen atom (chlorine, fluorine) with a=0 to 3,
an OH functional group with a=0 to 2.
the symbols R are identical or different and represent:
a phenyl radical substituted with at least one electron-attracting group such as for example OCF3, CF3, NO2, CN, and/or with at least 2 halogen atoms (fluorine most particularly), this being when the cationic entity is an onium of an element of groups 15 to 17.
a phenyl radical substituted with at least one element or one electron-attracting group, in particular a halogen atom (fluorine most particularly), CF3, OCF3, NO2, CN, this being when the cationic entity is an organometallic complex of an element of groups 4 to 10,
an aryl radical containing at least two aromatic nuclei such as for example biphenyl, naphthyl, optionally substituted with at least one electron-attracting group or element, in particular a halogen atom (fluorine most particularly), OCF3, CF3, NO2, CN, regardless of the cationic entity.
Without being limiting, more details are given below as regards the subclasses of onium borate and of borate of organometallic salts more particularly preferred in the context of the use in accordance with the invention.
According to a first preferred variant of the invention, the entity of the anionic borate entity which are most particularly suitable are the following: 
According to a second preferred variant of the invention, the onium salts (1) which can be used are described in numerous documents, in particular in patents U.S. Pat No. 4,026,705, U.S. Pat. No. 4,032,673, U.S. Pat. No. 4,069,056, U.S. Pat. No. 4,136,102, U.S. Pat. No. 4,173,476. Among these, the following cations will be most particularly preferred:
[("PHgr")2I]+ [C8H17xe2x80x94Oxe2x80x94"PHgr"xe2x80x94Ixe2x80x94"PHgr"]xe2x88x92 [("PHgr"xe2x80x94CH3)21]+[C12H25xe2x80x94"PHgr"xe2x80x94Ixe2x80x94"PHgr"]+ [(C8H17xe2x80x94Oxe2x80x94"PHgr")2I]+ [(C8H17xe2x80x94Oxe2x80x94"PHgr"xe2x80x94Ixe2x80x94"PHgr")]xe2x88x92[("PHgr")3S]+ [("PHgr")2xe2x80x94Sxe2x80x94"PHgr"xe2x80x94Oxe2x80x94C8H17]+[(CH3xe2x80x94"PHgr"xe2x80x94Ixe2x80x94"PHgr"xe2x80x94CH(CH3)2]+ , and [("PHgr"xe2x80x94Sxe2x80x94"PHgr"xe2x80x94Sxe2x80x94("PHgr")2]+ [(C12H25xe2x80x94"PHgr")2I]+ [(CH3"PHgr"xe2x80x94Ixe2x80x94"PHgr"xe2x80x94OC2H5]+;
According to a third preferred variant, the organometallic salts (4) which can be used are described in the documents U.S. Pat. No. 4,973,722, U.S. Pat. No. 4,992,572, EP-A-203 829, EP-A-323 584 and EP-A-354 181. The organometallic salts most readily selected according to the invention are in particular:
(xcex75-cyclopentadienyl) (xcex76-toluene) Fe+,
(xcex75-cyclopentadienyl) (xcex76-methyl-1-naphthalene) Fe+,
(xcex75-cyclopentadienyl) (xcex76-cumene) Fe+,
bis(xcex76-mesitylene) Fe+,
bis(xcex76-benzene) Crxe2x88x92.
In agreement with these three preferred variants, the following products may be mentioned by way of examples of photoinitiators of the onium borate type:
[("PHgr")2I]+.[B(C6F5)4]xe2x88x92 [(C8H17)xe2x80x94Oxe2x80x94"PHgr"xe2x80x94I"PHgr")]+.[B(C6F5)4]xe2x88x92[C12H25xe2x80x94"PHgr"xe2x80x94Ixe2x80x94"PHgr"]xe2x88x92, [B(C6F5)4]xe2x88x92 [(C8H17xe2x80x94Oxe2x80x94"PHgr")2I]+.[B(C6F5)4]xe2x88x92[(C8H17)xe2x80x94Oxe2x80x94"PHgr"xe2x80x94Ixe2x80x94"PHgr")]+, [B(C6F5)4]xe2x88x92 [("PHgr")3S]xe2x88x92,[B(C6F5)4]xe2x88x92[("PHgr")2Sxe2x80x94"PHgr"xe2x80x94Oxe2x80x94C8H17]+, [B(C6H4CF3)4]xe2x88x92[(C12H25xe2x80x94"PHgr")2I]xc2x0.[B(C6F5)4]xe2x88x92[("PHgr"3S]+,[B(C6F4OCF3)4]xe2x88x92 [("PHgr"xe2x80x94CH3)2I]+.[B(C6F5)4]xe2x88x92[("PHgr"xe2x80x94CH3)2I]+.[B(C6F4OCF3)4]xe2x88x92 [CH3xe2x80x94"PHgr"xe2x80x94I"PHgr"xe2x80x94CH(CH3)2]+.[B(C6F5)4]xe2x88x92
(xcex75-cyclopentadienyl) (xcex76-toluene) Fe+, [B(C6F5)4]xe2x88x92
(xcex75-cyclopentadienyl) (xcex76-methyl-1-naphthalene) Fe+, [B(C6F5)4]xe2x88x92
(xcex75-cyclopentadienyl) (xcex76-cumene) Fe+, [B(C6F5)4]
As another literary reference for defining the onium borates (1) and (2) and the borates of organometallic salts (4), there may be mentioned the entire content of patent applications EP 0 562 897 and 0 562 922. This content is integrally incorporated by reference into the present disclosure.
As another example of onium salt which can be used as photoinitator, there may be mentioned those disclosed in American patents U.S. Pat. No. 4,138,255 and U.S. Pat. No. 4,310,469.
Other cationic photoinitiators may also be used, e.g.:
those marketed by Union-Carbide (photoinitiator 6990 and 6974 triarylsulfonium hexafluorophosphate and hexafluoroantimonate),
the salts of iodonium hexafluorophosphate or hexafluoroantimonate,
or the ferrocenium salts of these various anions.
The nature of the photosensitizer contained in the dental composition according to the invention may be highly varied. In the context of the invention, it corresponds in particular to one of the following formulae (IV) to (XXII): 
formula (IV)
in which:
when n=1, Ar1 represents an aryl radical containing from 6 to 18 carbon atoms, a tetrahydronaphthyl, thienyl, pyridyl or furyl radical or a phenyl radical carrying one or more substituents chosen from the group consisting of F, Cl, Br, CN, OH, linear or branched C1-C12 alkyls, xe2x80x94CF3, xe2x80x94OR6, xe2x80x94OPhenyl, xe2x80x94SR6, xe2x80x94SPhenyl, xe2x80x94SO2Phenyl, xe2x80x94COOR6, xe2x80x94Oxe2x80x94(CH2xe2x80x94CHxe2x95x90CH2), xe2x80x94O(CH2H4xe2x80x94O)mxe2x80x94H, xe2x80x94O(C3H6O)mxe2x80x94H, m being between 1 and 100,
when n=2, Ar1 represents a C6-C12 arylene radical or a phenylene-T-phenylene radical where T represents xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94CH2xe2x80x94,
X represents a group xe2x80x94OR7 or xe2x80x94OSiR8(R9); or forms, with R4, a group xe2x80x94Oxe2x80x94CH(R10)xe2x80x94,
R4 represents a linear or branched C1-C8 alkyl radical which is unsubstituted or which carries an xe2x80x94OH, xe2x80x94OR6, C2-C8 acyloxy, xe2x80x94CF3 or xe2x80x94CN group, a C3 or C4 alkenyl radical, a C6 to C16 aryl radical, a C7 to C9 phenylalkyl radical,
R5 has one of the meanings given for R4 or represents a radical xe2x80x94CH2CH2R11, or alternatively forms with R4 a C1-C8 alkylene radical or a C3-C9 oxa-alkylene or aza-alkylene radical,
R6 represents a lower alkyl radical containing from 1 to 12 carbon atoms,
R7 represents a hydrogen atom, a C1-C12 alkyl radical, a C2-C6 alkyl radical carrying an xe2x80x94OH, xe2x80x94OR6 or xe2x80x94CN group, a C3-C6 alkenyl radical, a cyclohexyl or benzyl radical, a phenyl radical optionally substituted with a chlorine atom or a linear or branched C1-C12 alkyl radical, or a 2-tetrahydropyranyl radical,
R8 and R9 are identical or different and each represent a C1-C4 alkyl radical or a phenyl radical,
R10 represents a hydrogen atom, C1-C6 alkyl radical or a phenyl radical,
R11 represents a radical xe2x80x94CONH2, xe2x80x94CONHR6, xe2x80x94CON(R6)2, xe2x80x94P(O) (OR6)1 or 2-pyridyl; 
formula (V)
in which:
Ar2 has the same meaning as Ar1 of formula (IV) in the case where n=1,
R15 represents a radical chosen from the group consisting of a radical Ar2, a linear or branched C1-C12 alkyl radical, a C6-C12 cycloalkyl radical, and a cycloalkyl radical forming a C6-C12 ring with the carbon of the ketone or a carbon of the radical Ar2, it being possible for these radicals to be substituted with one or more substituents chosen from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94CN, xe2x80x94OH, xe2x80x94CF3, xe2x80x94OR6, xe2x80x94SR6, xe2x80x94COOR8, the linear or branched C1-C11 alkyl radicals optionally carrying an xe2x80x94OH, xe2x80x94OR6 and/or xe2x80x94CN group, and the linear or branched C1-C8 alkenyl radicals; 
formula (VI)
in which:
Ar3 has the same meaning as Ar1 of formula (IV) in the case where n=1,
R16, identical or different, represents a radical chosen from the group consisting of a radical Ar3, a radical xe2x80x94(Cxe2x95x90O)xe2x80x94Ar3, a linear or branched C1-C12 alkyl radical, a C6-C12 cycloalkyl radical, it being possible for these radicals to be substituted with one or more substituents chosen from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94CN, xe2x80x94OH, xe2x80x94CF3, xe2x80x94OR6, xe2x80x94SR6, xe2x80x94COOR5, the linear or branched C1-C12 alkyl radicals optionally carrying an xe2x80x94OH, xe2x80x94OR6 and/or xe2x80x94CN group, and the linear or branched C1-C8 alkenyl radicals; 
formula (VII)
in which:
R5, which are identical or different, have the same meanings as in formula (III),
Y, which are identical or different, represent X and/or R4,
Z represents:
a direct bond,
a C1-C6 divalent alkylene radical, or a phenylene, diphenylene or phenylene-T-phenylene radical, or alternatively forms, with the two substituents R5 and the two carbon atoms carrying these substituents, a cyclopentane or cyclohexane nucleus,
a divalent group xe2x80x94Oxe2x80x94R11xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94SiR5R3xe2x80x94Oxe2x80x94SiR5R3xe2x80x94Oxe2x80x94, or xe2x80x94Oxe2x80x94SiR6R9xe2x80x94Oxe2x80x94,
R12 represents a C1-C5 alkylene, C4-C6 alkenylene or xylylene radical, and Ar4 has the same meaning as Ar1 of formula (IV) in the case where n=1,
family of thioxanthones of formula (VIII): 
m=0 to 8,
R17, identical or different substituent(s) on the aromatic nucleus (nuclei), represent a linear or branched C1-C12 alkyl radical, a C6-C12 cycloalkyl radical, a radical Ar1, a halogen atom, an xe2x80x94OH, xe2x80x94CN, xe2x80x94NO2, xe2x80x94COOR6, xe2x80x94CHO, Ophenyl, xe2x80x94CF3, xe2x80x94SR6, xe2x80x94Sphenyl, xe2x80x94SO2phenyl, Oalkenyl, or xe2x80x94SiR63 group.
family of xanthenes of formula (IX): 
family of xanthones of formula (X): 
family of the naphthalene of formula (XI): 
family of the anthracene of formula (XII): 
family of the phenanthrene of formula (XIII): 
family of the pyrene of formula (XIV): 
family of the fluorene of formula (XV): 
family of the fluoranthene of formula (XVI): 
family of the chrysene of formula (XVII): 
family of the fluorene of formula (XVIII): 
family of the chromone of formula (XIX): 
family of the eosin of formula (XX): 
family of the erythrosin of formula (XXI): 
family of the biscoumarins of formula (XXII): 
R18, identical or different, has the same meaning as R17 or represents a group xe2x80x94NR62, for example 3,3xe2x80x2-carbonylbis(7-diethylaminocoumarin) and 3,3xe2x80x2-carbonyl-bis(7-methoxycoumarin).
Other sensitizers can be used. In particular, the photosensitizers described in the documents U.S. Pat. No. 4,939,069; U.S. Pat. No. 4,278,751; U.S. Pat. No. 4,147,552 may be used.
In the context of the present invention, the photosensitizers have a residual absorption of UV light between 200 and 500 nm, preferably 400 to 500 nm for the preparations of dental prostheses. For dental restoration, a photosensitizer having a residual absorption of UV light above 400 nm will be preferred.
According to a preferred variant, the photosensitizers will be chosen from those of the families (IV), (VII) and (VIII). By way of examples, the following photosensitizers will be mentioned:
4,4xe2x80x2-dimethoxybenzoin; 2,-4-diethylthioxanthone 2-ethylanthraquinone; 2-methylanthraquinone; 1,8-dihydroxyanthraquinone; dibenzoylperoxide; 2,2-dimethoxy-2-phenylacetophenone; benzoin; 2-hydroxy-2-methylpropiophenone; benzaldehyde; 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)-ketone; benzoylacetone; 
xe2x80x832-isopropylthioxanthone; 1-chloro-4-propoxythioxanthone; 4-isopropylthioxanthone; and the mixture thereof.
Various types of fillers can be used for preparing the compositions according to the invention. The fillers are chosen according to the final use of the dental composition; these affect important properties such as appearance, penetration of UV radiation, as well as the mechanical and physical properties of the material obtained after crosslinking and/or polymerization of the dental composition.
As reinforcing filler, there may be used treated or untreated pyrogenic silica fillers, amorphous silica fillers, quartz, glass or nonglassy fillers based on oxides of zirconium, barium, calcium, fluorine, aluminum, titanium, zinc, borosilicates, aluminosilicates, talc, sperosil, yterbium trifluoride, fillers based on polymers in ground powder form, such as inert or functionalized methyl polymethacrylates, polyepoxides or polycarbonates.
By way of example, there may be mentioned:
inert fillers based on methyl polymethacrylate LUXASELF from the company UGL, which can be used in the dental field and which are pigmented in pink,
hexamethyldisilazane-treated fumed silica fillers having a specific surface area of 200 m2/g,
untreated fumed silica fillers (xe2x80x9caerosilxe2x80x9d AE200 marketed by SEGUSSA).
According to an advantageous variant of the invention, the fillers and in particular the silica fillers are treated before use at 120xc2x0 C. with a quantity of less than 10% w/w of silicone comprising at least one unit of formula (XXIII):
Zxe2x80x94Si"Parenopenst"R0"Parenclosest"2O(3-a)/2
such that Zxe2x80x2 has the same definition as Zxe2x88x92a=0,1,2 or 3
with at least one silicon atom.
There may be mentioned by way of example the polymer described below with Z=epoxide and Z=trialkoxysilyl 
In this case for the treatment of silicone-containing filler(s), in particular silica, with this type of polymer, the material obtained after crosslinking has a mechanical strength, a modulus of elasticity and a resistance to compression which are markedly improved.
In addition to the reinforcing fillers, pigments may be used to color the dental composition according to the invention envisaged and the ethnic groups.
For example, red pigments are used in the presence of microfibers for the dental compositions used for the preparation of dental prostheses in order to simulate the blood vessels.
Pigments based on metal oxides (iron and/or titanium and/or aluminum and/or zirconium oxides, and the like) are also used for the dental compositions used for the preparation of restoration material, in order to obtain a crosslinked material having an ivory color.
Other additives may be incorporated into the dental compositions according to the invention. For example, biocides, stabilizers, flavoring agents, plasticizers and adherence promoters.
Among the additives which may be envisaged, there will be advantageously used crosslinkable and/or polymerizable coreagents of the organic type. These coreagents are liquid at room temperature or are hot-meltable at a temperature of less than 100xc2x0 C., and each coreagent comprises at least two reactive functional groups such as oxetane-alkoxy, oxetane-hydroxyl, oxetane-alkoxysilyl, carboxyl-oxetane, oxetane-oxetane, alkenyl ether-hydroxyl, alkenyl ether-alkoxysilyl, epoxy-alkoxy, epoxy-alkoxysilyls, dioxolane-dioxolane-alcohol, and the like.
The dental compositions according to the invention may be used for numerous dental applications, and in particular in the field of dental prostheses, in the field of dental restoration and in the field of temporary teeth.
The dental composition according to the invention is preferably provided in the form of a single product containing the various components (xe2x80x9cmonocomponentxe2x80x9d) which facilitates its use, in particular in the field of dental prostheses. Optionally, the stability of this product may be provided for by organic derivatives with amine functional groups according to he teaching of the document WO 98/07798.
In the field of dental prostheses, the product in the xe2x80x9cmonocomponentxe2x80x9d form may be deposited with the aid of a syringe directly on the plaster model or in a core. Next, it is polymerized (polymerization by possible successive layers) with the aid of a UV lamp (visible light spectrum 200-500 nm).
In general, it is possible to produce a lasting and esthetic dental prosthesis in 10 to 15 min.
It should be noted that the products obtained from the dental composition according to the invention are nonporous. Thus, after an optional polishing with the aid of a felt brush, for example, the surface of the dental prostheses obtained is smooth and bright and therefore does not require the use of varnish.
The applications in the field of dental prostheses are essentially those of the joined prosthesis, which can be divided into two types:
full prosthesis in the case of a patient with absolutely no teeth
partial prosthesis due to the absence of several teeth, resulting either in a provisional prosthesis, or a skeleton brace.
In the field of dental restoration, the dental composition according to the invention may be used as material for filling the anterior and posterior teeth in different colors (for example xe2x80x9cVITAxe2x80x9d colors), which is rapid and easy to use.
The dental composition being nontoxic and polymerizable in thick layers, it is not essential to polymerize the material in successive layers. In general, a single injection of the dental composition is sufficient.
The preparations for dental prostheses and for restoration materials are carried out according to techniques which are customary in the art.
In the case of application of the dental composition as a tooth, either the tooth may be pretreated with a bonding primer or the dental composition may be prepared as a mixture with a bonding primer before its use. However, it is not essential to use a bonding primer in order to use the dental composition according to the invention.
The following examples and tests are given by way of illustration. They make it possible in particular to understand more clearly the invention and to highlight some of its advantages and to illustrate a few of its variant embodiments.